Electromagnetic clutch apparatus

Abstract

An electromagnetic clutch apparatus for providing a reversible mechanical linkage between a driving motor and its mechanical load and which is particularly well suited for use as part of an electrically actuatable automotive cruise control system. The apparatus is inherently self-disengaging, thereby limiting the maximum mechanical load against which the driving motor may operate. The apparatus is designed to be placed between the final output gear of a gear train and the engine throttle and yet overcomes the problems associated with such a placement because the mechanical torque which the clutch is designed to transmit is not directly related to the electromagnetic force required to keep the clutch engaged.

What is claimed is: 
     
       1. A clutch apparatus of the positive engagement type for reversibly enabling a mechanical linkage between a driving motor and said motor's mechanical load utilizing a differential gear cluster comprising: a driving bevel gear mechanically connected to said driving motor and rotating about a fixed axis means;   a driven bevel gear mechanically connected to a mechanical load and also rotating about said fixed axis means;   an interposing gear with teeth meshing with the teeth of both said driving bevel gear and said driven bevel gear and rotating about a rotatable axis means perpendicular to said fixed axis means in such manner as to impart no torque to said driven gear as said interposing gear is made to rotate by said driving gear if said rotatable axis is free to rotate about said fixed axis; and   a mechanical stop means for reversibly enabling and disabling the free rotation of said rotatable axis means about said fixed axis means thereby reversibly disabling and enabling, respectively, the mechanical linkage between said driving gear and said driven gear.   
     
     
       2. The apparatus of claim 1 wherein said mechanical stop means further comprises a mechanical switch means which limits the force which said mechanical stop means can apply to said rotatable axis means in preventing the rotation of said rotatable axis means about said fixed axis means. 
     
     
       3. The apparatus of claim 2 wherein said mechanical switch means further comprises an electric solenoid means which maintains said mechanical stop means in position to prevent rotation of said rotatable axis means about said fixed axis means until a force is applied by said rotatable axis means to said mechanical stop means which overcomes the maximum electromagnetic holding force of said solenoid means. 
     
     
       4. The apparatus of claim 3 wherein said mechanical switch means further comprises: a rotatable engagement shaft oriented perpendicularly to the plane in which said rotatable axis means rotates about said fixed axis means;   a lever means either attached to, or integrally a part of, said engagement shaft which makes contact with said distal end of said rotatable axis means at a single point in said distal end's path of rotation so as to prevent the further rotation of said rotatable axis means about said fixed axis means while enabling said distal end to apply a torque tending to rotate said engagement shaft abouts its longitudinal axis, and, when said engagement shaft is so rotated, said lever means being positioned and constructed so as not to inhibit the further rotation of said rotatable axis means about said fixed axis means; and   a cable means attached to said engagement shaft and attached to said solenoid means in such manner that a torque is applied to said engagement shaft by said solenoid means through said cable means which is in an opposite direction to the torque applied to said engagement shaft by said distal end of said rotatable axis means which maintains said lever means in position to prevent rotation of said rotatable axis means about said fixed axis means until the torque applied to said rotatable shaft by said distal end of said rotatable axis means exceeds the maximum torque which can be applied to said rotatable shaft by said solenoid means.   
     
     
       5. An apparatus for actuating the throttle of a motor vehicle as part of, for example, an automatic speed control system, comprising: a driving motor;   the clutch apparatus of claim 1;   a mechanical pulley mechanically connected to said driven gear;   a cable means attached to both the throttle of the motor vehicle and said mechanical pulley in such manner that rotation of said mechanical pulley in a direction which retracts said cable means results in motion of the vehicle's throttle in a direction which tends to increase the vehicle's speed;   a spring means connected to said mechanical pulley at one end and immovably fixed at the other end, oriented so as to cause said mechanical pulley to rotate in a direction which lessens the tension in said cable means attaching said mechanical pulley to the vehicle's throttle; and   a mechanical stop means which stops the rotation of said mechanical pulley due to the torque produced by said spring means at a point at which the vehicle's throttle is in an appropriate idling position.   
     
     
       6. The apparatus of claim 5 further comprising: a retaining lug attached to said cable means attaching the vehicle's throttle to said mechanical pulley wherein said retaining lug is slideably engaged in a pathway of said mechanical pulley;   a mechanical stop means which limits the sliding of said retaining lug and enables said mechanical pulley to produce tension in said cable means attached to the vehicle's throttle upon rotation in the appropriate direction;   a pathway, integrally a part of said mechanical pulley, into which said retaining lug is slideably engaged in such manner as to allow said retaining lug to slide in a direction which prevents excessive slack from forming in said cable means upon the motion of said cable means toward said mechanical pulley.   
     
     
       7. An apparatus for actuating the throttle of a motor vehicle as part of, for example, an automatic speed control system, comprising: a driving motor;   the clutch apparatus of claim 4;   a mechanical pulley mechanically connected to said driven gear;   a cable means attached to both the throttle of the motor vehicle and said mechanical pulley in such manner that rotation of said mechanical pulley in a direction which retracts said cable means results in motion of the vehicle's throttle in a direction which tends to increase the vehicle's speed;   a spring means connected to said mechanical pulley at one end and immovably fixed at the other end, oriented so as to cause said mechanical pulley to rotate in a direction which lessens the tension in said cable means attaching said mechanical pulley to the vehicle's throttle; and   a mechanical stop means which stops the rotation of said mechanical pulley due to the torque produced by said spring means at a point at which the vehicle's throttle is in an appropriate idling position.